Removal of deposits such as paraffin from oil lines by use of soluble candy plug



Q March 3, 1959 J. GS'GLEQNNEY 2,876,145 REMOVAL OF DEPOSITS SUCH AS PARAFFIN FROM OIL.

LINES BY USE OF SOLUBLE CANDY PLUG 2 Sheets-She 'et 1 med larch 25, 1957 March 3, 1959, J.- G. GLENNEY 2,876,145

REMOVAL OF DEPOSITS SUCH ,AS PARAFFIN FROM OIL LINES BY USE OF SOLUBIZE CANDY PLUG Filed March 25, 1957 2 Sheets-Sheet 2 as a production unit United States Patent REMOVAL OF DEPOSITS SUCH FROM OIL LINES BY USE CANDY PLUG Julius G. Glenney, Pampa, Ten,

Company, New York, N.'Y.,

ware

Application March 25, 1957, Serial No. 648,108 7 Claims- (Cl. 134-8) AS PARAFFIN OF SOLUBLE assignmto The Texas a corporation of Dela- This invention relates generally to the cleaning of the internal surface of oil carrying conduits and, in one of its more specific aspects, relates to a method for the removal of deposits of paratlin and allied hydrocarbons from the inner surfaces of conduits carrying pressurized oil to a fluid engine.

In certain well pumping operations, the bottom hole pump for the hydraulic pumping system is referred to and consists of a hydraulic engine a displacement pump. The hydraulic engine is located at the top end of the production unit and consists of a double acting, reciprocating engine piston whose motion is controlled by a hydraulically actuated valve and which is driven and lubricated by power oil transmitted by tubing from a surface pump direct to the engine in the well.

The pump is at the lower end of the production unit and consists of a double acting, reciprocating piston connected directly to the engine piston. The intake of the pump is located at the bottom end of the production unit which is seated in a shoe in the production tubing or well casing. The pump exhausts into the annular passage between the pump and the production tubing or well casing. Since the hydraulic power fluid used to operate the production unit is crude oil drawn off from the surface tank battery, it is feasible to allow the exhausted power oil from the engine to be discharged into the pumped production fluid.

The surface equipment of the hydraulic pumping system includes the following elements: a storage tank battery including a settling tank into which the production fluid, i. e. crude oil, is directed and from which the power oil is drawn from the top part of the settling tank, a power oil line leading from the latter to a pump assembly for pressurizing the fluid to be provided the hydraulic engine of the production unit, power line pipe, usually of about 1" internal diameter, leading from the pump assembly to a manifold at the power control station for control of the rate of flow of the power oil to regulate the pump speed in each of a battery of producing wells, the manifold including means for the insertion of a clean-out device and being joined to power tubing, of about %"internal diameter, the latter leading the power oil to the production unit in the well.

Certain crude petroleum oils contain a large proportion of paraflin and allied hydrocarbons. The presence of these in conduits carrying crude oils presents a serious problem when the oils congeal, and especially during periods of lower ambient temperatures. When such matter is deposited in the conduits and as the-accumulation of paraffin or other substances progresses, the flow of oil is impeded and eventually the conduit clogs. A reasonable bottom hole temperature of the environment in which the production unit operates is about 120 F., sufiiciently high to permit free flow of crude oil with a large paraifin content. The temperature drop from the production zone of the well through the storage tank battery and settling tank is not enough usually to impede fluid connected directly to ing deposits 2 flow in the production tubing or other conduits. However, trouble is encountered after the fluid, which is now being used as power oil, passes the valve restrictions of the flow control manifold. Not only is there a pressure drop due to a division of the flow of pressurized fuel, but considerable distances of flow from the manifold to the oil well casing head allow for further cooling, a condition which is conductive to deposit accumulation in ICC the power oil lines. When these are exposed on the surface and become clogged, they may be treated easily by applying heat in order to dispose of the paraffin or other deposits by solution in the power oil. This feature cannot exist with the power oil tubing which is joined to the power oil line and is suspended from the well casing head within the producing well. The temperature drop conditions prevail for a distance within the well and until this region is reached and passed by the cooled power oil, deposit formation on the inner surface of the conduit continues, so that the efficiency of the pumping system diminishes unless the power oil line pipe tubing is cleared periodically of deposits formed-therein.

Attempts to developa satisfactory method for removof paraffin and the like from the production pipe and tubing have not proved completely satisfactory. In the case of'the removal of power tubing from the well for cleaning, e.- g. by scraping, the well is required to be shut down for some time, leading to an expensive operation. An insoluble body, forced through the tubing to scrape deposits from the inner surface of the tubing, could cause damage to the engine of the production unit, or at least would plug the tubing so that the production unit could not be operated.

In case a soluble plug is used for the parafiin removal, e. g. a naphthalene ball, as disclosed in the coassigned U. S. Patent No. 2,411,044, the problem of dissolving too quickly in the crude oil arises at times, the ball may not pass far enough through the power oil line to clean it of the deposited material even when followed with a slug of fluid capable of retarding the dissolving action of the crude oil on the ball. Should the naphthalene ball be coated with a material not as soluble, on occasion, the coating of the soluble plugs has not dissolved to the required extent so that the production unit and power oil lines have become clogged, necessitating pulling of the subsurface well equipment, thus increasing expenses in addition to the relatively high cost of the coated soluble plugs. In accordance with the present invention, a soluble plug has been found now which is slower dissolving than the prior art naphthalene plug and does not require any follower slug of saturated fluid, is considerably less expensive than other soluble or coated plugs in current use, and has no deleterious effect on the production fluid.

A principal object of the invention is to provide an improved method for the removal of deposits from the inner surface of a conduit conducting pressurized oil to a hydraulic engine during its normal operation and without having any detrimental effect either on the power oil or the mechanism of the production unit.

Still another object of invention is an improved method which is useful in removing deposits from conduits carrying oil having a high paraflin content and the like and which tend to restrict fluid flow with operating temperature changes.

And another object of invention is to provide a method whereby parafiin deposits and the like can be removed easily from pipe and tubing supplying power oil to a production unit of a hydraulic pumping system without disassembly thereof and without causing any damage to the mechanism of the engine or well pump.

These and other objects and advantages of the invention will become apparent from the following description when taken in conjunction with the following drawings wherein:

Fig. 1 is a diagrammatic showing of part of the surface installation for use with the present invention;

Fig. 2 is an enlarged diagrammatic showing of part of the power control station;

Fig. 3 is a vertical elevation partly in section through a production well being pumped by means of a hydraulic production unit;

Fig. 4 is a sectional elevation through a portion of the power tubing showing one of the cleaning devices of the present invention being forced through the tubing for removal of deposited paraflin which has accumulated therein. 7

The improved device, and its method of utilization in clearing out unwanted deposits in a hydraulic pumping system comprises a solid body having a spheroidal configuration confonming in size to that of the inner contour of a power line and being suificiently soluble in the contents of the production fluid, without having any deleterious effects on it or the pumping equipment and of hardness sulficient to be worn down with normal usage of scraping, so that a single unit of the device may be pumped through a power line of differing and lessening internal dimensions without necessity of shut down of the unit for the insertion of smaller clean out plugs. Such requirements are satified by ordinary hard round candy, known commonly as jaw breakers.

Referring to Fig. 1 of the drawing, the Surface installation comprises a storage tankbattery wherein a settling tank is indicated at T, a power oil line indicated by L leading from the top part of the tank and ending at a pump assembly P. The power oil line leading from the pump assembly P and carrying the pressurized power oil is indicated at L and is connected to a well manifold of a power control station indicated respectively at M and S. This station includes conventional valves indicated at V, pressure gauges indicated at G, and traps indicated at R, for the insertion of a clean-out plug for use in the removal of unwanted deposits in the power oil lines. After leaving the well manifold, the power oil line pipe 10 (of about 1" internal diameter) is joined to power oil tubing 11 (of about internal diameter) at the casing head 12, closing the top of the production well, the production fluid, e. g. oil, being lead off by production tubing F discharging into the settling tank T. The production gas is led ofi to a suitable reservoir by the tubing indicated at G. The pipe 10 and tubing 11 are considered as the progressively smaller elements of the power oil line.

In Fig. 3, a well hole 20, leading to the producing formation 21, is provided with a casing 22 held in position, as by cement, at 23. A string of production tubing 13 is shown suspended within the well hole, held in position by the casing head 12. The well production unit (or pump) anchor is shown at 24, disposed at the lower end of the production tubing string, and secured to this anchor is the production unit 25, attached to the end of the string of power oil tubing 11, and comprising the fluid pressure engine joined to the well pump. The fluid pressure engine is actuated by the power oil provided through the power oil tubing 11 from the pump assembly P at the surface, with the exhaust of pressurized oil being discharged into the production zone and allowed to mix with the production fluid, which flows upwardly to the surface through the production tubing 13. The operation of the production unit as described above is well known to the art and the apparatus therefor is a standard piece of equipment in petroleum production.

As shown more clearly in Fig. 4, a deposit of paraffin or like material may adhere to the inner surface of the power oil tubing and because of its small diameter, even a thin layer of such a deposit is sufficient to reduce materially the efliciency of the production unit. In order to remove this deposit without closing down the production system, a body 26 of spheroidal configuration is placed in the power oil line pipe loand is forced to the casing head and through tubing with the pressurized oil on its way to the production unit. This body may be inserted into the power oil line pipe (or tubing) in any suitable manner and is indicated here by use of a Y-trap at R. As the spheroidal body passes through the power oil line pipe 10, Fig. 2 to the tubing 11, Fig. 4, the deposit 27 (of paratfin or the like) is scraped from the tubing wall and passes downwardly to and throughout the fluid pressure engine of the production unit. At the inlet end to the engine of the production unit, there is provided a strainer or screen 28 to prevent sand or other foreign substances which might be carried by the power oil from entering, as well as retaining large pieces of deposited material and the undissolved body.

A spheroidal body having the required characteristics and properties is found among hard candy balls commonly known as jaw breakers." This type of hard candy ball conforms in general size and shape to the inner contour of the power oil lines and dissolves and disintegrates possibly by abrasion in its passage through the power oil lines. Should the body reach the intake of the engine of the production unit before it has been dissolved completely, it will be held back by the strainer at 28, and the flow of pressurized oil past the body will dissolve it very quickly, with the resulting solution passing through the engine and being exhausted into the production fluid. The sugar content of the jaw breakers" does not prevent deposit of paraffin nor aid in its removal from the metal surface, which is accomplished by the swabbing action in the power oil lines, provided the candy ball is of the proper size. Not only is the solubility of the jaw breakers" in oil almost exactly that required to give the best results, being slower than the prior art soluble plug, but the cost per unit plug is less than one cent as compared with an average price of approximately fifteen cents for a less satisfactory prior art plug.

The method of manufacture is well known and briefly comprises the building up of a jaw breaker, by tumbling action, of a number of layers of a solution including sugar, corn syrup, artificial flavoring and food coloring, until a ball of generally one inch diameter is obtained. The jaw breakers" used in this invention are not truly round, having a short diameter of about ,4 inch and a long diameter of about inch, which is too large for use with the tubing. Where the power oil lines are extensive, they may consist of a power oil pipe of about one inch diameter and power oil tubing of about inch diameter. Consequently this size jaw breaker works satisfactory in these power oil lines since it is reduced in size by solution in the power oilpipe and by abrasion during its travel from the trap at the control station manifold to the well casing head where the tubing is joined, so that by the time the power oil tubing is reached, the candy jaw breaker is small enough to pass through it. The "jaw breaker in its passage through the tubing will dissolve and disintegrate further in the presence of the oil within the tubing and, in normal operation, will disintegrate almost completely before it reaches the strainer at the top of the production unit. Otherwise, it will lodge against the strainer, and its solution and disintegration will follow much more rapidly due to the turbulence of the oil flowing past.

Although it is preferred to use candy jaw breakers," other solid balls of sugar compounds, such as the ordinary hard candy known as sour balls, may be used, when they have the comparable qualities, e. g. size, hardness and solubility. These sour balls" and the like are formed or molded from glossy sugar solutions, being amorphous and usually transparent and translucent. In test, the hardness of a satisfactory clean out plug comprising a candy ball has been determined to be about 2.5 on the Mohs scale, a value lying between that of gypsum and calcite. The solubility is due to the small amount of water in the crude oil, with the process being aided by the relatively elevated ambient temperatures.

Laboratory tests under simulated pumping operation indicates but a negligible amount of solution in dry oil and that a 30% reduction in the weight of the soluble body follows rapidly in the presence of added brine. Where the problem o too rapid a solution of the clean out plug arises due to the extent of the power oil lines, the method of using a saturated plug of power oil, as disclosed in the above cited patent, is available for retarding such action. Due account should be allowed for the reduction of the candy ball in its travel through the power oil lines because of abrasion with the inner wall.

Thus, it will be seen that a method has been devised by means of which a deposit of parafiin or the like can be easily and quickly removed from the internal surfaces of power oil lines to restore full fiow therein during actual well pumping operation, without necessity to shut down the pump for removal of the power oil lines for cleaning. With the apparatus as shown, it is necessary to stop the pump operation for a short period of time in order that the soluble plug or candy ball may be inserted into the power oil line. Any suitable trap device could be used in place of the disclosed Y-trap at R, in order to place the candy ball in the stream of oil without losing any of the oil, e. g., when a soluble plug 26 is to be inserted into the power oil pipe at 10, Fig. 2, both-valves V are closed while the trap cover at R is being manipulated.

Although the invention has been described with particular reference to the cleaning out of the power oil pipe and tubing of an oil well production unit, it is believed evident that the same method can be used in cleaning surface pipelines and also is not. to be limited to the removal of paraffin from an oil conducting conduit.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims,

I claim:

1. In a well pumping operation utilizing a bottom hole hydraulic engine pumping system, the method of removing a deposit formation from the inner surface of a power oil conducting means having progressively lesser inner dimensions as said pumping system is approached which comprises forcing through said means with said power oil a substantially solid body of hard candy smaller than the inner dimensions of said means starting at the larger inner dimension thereof, said body being reduced during its passage through said means, the reduction of said body resulting from dissolution in and abrasion by said power oil within said means.

2. In the method as defined in claim 1, said body of hard candy comprising a soluble plug having a hardness value lying between that of gypsum and calcite, and being soluble in the production fluid being pumped.

3. In the method as defined in claim 2, said body comprising a substantially round, hard candy ball formed by the build up of successive layers of a sugar solution.

4. In the method as defined in claim 2, said body comprising a hard, substantially round ball of candy molded from a glossy sugar solution.

5. In the operation of a hydraulic well pumping system having a bottom hole pump and utilizing as power oil part of the production fluid, the method of removing a deposit adhering to the internal surface of a power oil conduit having elements of progressively lesser inside diameters leading to said pump which comprises fo.c ing through the element having the larger inside diameter a solid body of hard candy slightly smaller than the inside diameter of the last mentioned element of said conduit, said body being reduced progressively in dimension to be accommodated within said conduit so that by the time said solid body has traveled to an element of lesser inside diameter, a reduction has been obtained by disintegration thereof from solution in said power oil and by abrasion within said conduit and said solid body fits therewithin for removal of said deposit by a plug swabbing action.

6. In the method as defined in claim 5, said body of hard candy having a hardness of about 2.5 on the Mohs scale.

7. The method of removing a deposit from the inner surface of an oil conducting means which comprises forcing with oil through said oil conducting means solid bodies of hard candy substantially smaller than the inside thereof, said bodies being reduced in size during their passage through said oil conducting means, the reduction of said bodies resulting from dissolution in oil and by abrasion due to contact with the inner surface of said oil conducting means.

References Cited in the file of this patent UNITED STATES PATENTS 2,352,805 Scheuermann July 4, 1944 2,411,044 Landrum Nov. 12, 1946 2,603,804 Billhartz July 22, 1952 2,744,880 Brown May 8, 1956 

7. THE METHOD OF REMOVING A DEPOSIT FROM THE INNER SURFACE OF AN OIL CONDUCTING MEANS WHICH COMPRISES FORCING WITH OIL THROUGH SAID OIL CONDUCTING MEANS SOLID BODIES OF HARD CANDY SUBSTANTIALLY SMALLER THAN THE INSIDE THEREOF, SAID BODIES BEING REDUCED IN SIZE DURING THEIR PASSAGE THROUGH SAID OIL CONDUCTING MEANS, THE REDUCTION OF SAID BODIES RESULTING FROM DISSOLUTION IN OIL AND BY ABRASION DUE TO CONTACT WITH THE INNER SURFACE OF SAID OIL CONDUCTING MEANS. 